The human body is complex, I don't think it follows any arithmetic logic when processing food, I have fasted one time more than 33 hours or so, with nothing but water, and yet my body weight didn't show any changes after a week, fasting 33hours should be like an earthquake in my body memory, but there was no one single trace of that earthquake on my body weight data.

It's not a question of arithmetic but just a particular organ's ability to function differently. It happens for all other organs (within bounds) as they become conditioned to whatever regular conditions they are placed in. I don't think there is one particular dividing line but just saying that in general if your system is used to taking in 1500-1600 calories, which the average sedentary woman would be doing, and suddenly try to force through that same system over 3x that many there is a good probability that many of that food is going to get pushed through undigested, assuming it goes down in the first place.

You can't look at weight fluctuations over a one or two day period and try to track meaningful fat loss/gain over that period. Deviations from day to day based on how much is in your digestive system, levels of water retention, et cetera can create multi-pound weight swings. I know they do for me anyway. If you are tracking all your calories and activities rigorously over a longer period of time, let's say 1 month, and look at the variation in your weight and body composition to see what the total fat and lean muscle mass loss are you should be able to get to get pretty close, including with a 33 hour fast in there.